head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Competitive PvP
Reversal timing and pacing against an opponent baiting your counters.

Execution · Competitive PvP
Reversal-timing wrestling exchanges with a thin layer of versus-human guessing.
WWE 2K15 leans Execution (Competitive PvP); WWE Legends of WrestleMania leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
WWE 2K15
Reversal timing windows decide most exchanges
WWE Legends of WrestleMania
Grapple chains and reversal timing windows decide exchanges
WWE 2K15 leans a little harder on reads, though the gap is small.
WWE 2K15
Human opponents bait reversals and vary move timing
WWE Legends of WrestleMania
Versus humans, guessing reversal attempts adds a thin mind game
WWE 2K15 leans a little harder on variance, though the gap is small.
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
WWE Legends of WrestleMania
Outcomes follow inputs with little randomness
WWE 2K15 leans a little harder on optimization, though the gap is small.
WWE 2K15
Move sets, stamina and match pacing are learnable systems
WWE Legends of WrestleMania
Move chains and match-type knowledge are shallow but present
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.